Learn Italian: Gli zaini degli studenti sono pesanti. - The students' backpacks are heavy.

degli is a combination of the preposition di (of) and the article gli (the). We must use gli because studenti is a masculine plural word starting with an 's' plus a consonant ('t'). When you combine di + gli, it forms degli.

The translation says "The students' backpacks", but why is the Italian word order backward?

Italian doesn't have an apostrophe-'s' to show ownership. Instead, you always phrase it as "the something of someone". So, "the students' backpacks" literally becomes "the backpacks of the students" (gli zaini degli studenti).

Why is the article gli used for zaini instead of the usual plural i?

Masculine nouns have special articles depending on their first letters. For words starting with a 'z' (like zaino), or an 's' plus a consonant, the plural article is always gli.

Why does the adjective pesanti end in -i?

It is plural to match zaini. The dictionary form of "heavy" is pesante. Adjectives that end in -e in the singular always change to -i in the plural, regardless of whether the noun they describe is masculine or feminine.